U.S. patent application number 13/219385 was filed with the patent office on 2012-03-29 for wound dressings.
Invention is credited to Philip Andrews, Robert Halstead, Hugh Semple Munro, David Preece, Malcolm Russell.
Application Number | 20120078153 13/219385 |
Document ID | / |
Family ID | 44862425 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120078153 |
Kind Code |
A1 |
Russell; Malcolm ; et
al. |
March 29, 2012 |
WOUND DRESSINGS
Abstract
A dressing for covering a wound of a patient comprises a sheet
member adapted to be adhered to the patient's skin in use to
provide an airtight seal around the wound, wherein the
skin-adhesion is provided by a hydrogel layer 10 on the skin-facing
face of the sheet member, wherein the sheet member defines in use a
substantially enclosed space 5 above the wound, and wherein a
plurality of mutually spaced-apart flutter valves formed by holes 5
in a thin film 13 overlying an upper face of a layer 12 of the
sheet member permit one-way air, blood and/or other fluid flow
communication from the space 5 above the wound to the exterior of
the dressing.
Inventors: |
Russell; Malcolm;
(Herefordshire, GB) ; Andrews; Philip; (Wiltshire,
GB) ; Munro; Hugh Semple; (Wiltshire, GB) ;
Halstead; Robert; (Wiltshire, GB) ; Preece;
David; (Herefordshire, GB) |
Family ID: |
44862425 |
Appl. No.: |
13/219385 |
Filed: |
August 26, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61377373 |
Aug 26, 2010 |
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Current U.S.
Class: |
602/43 |
Current CPC
Class: |
A61F 13/023 20130101;
A61F 13/0226 20130101; A61F 13/0253 20130101; A61F 13/0213
20130101; A61F 13/00068 20130101; A61F 2013/00165 20130101 |
Class at
Publication: |
602/43 |
International
Class: |
A61F 13/02 20060101
A61F013/02 |
Claims
1-21. (canceled)
22. A dressing for covering a wound of a patient, comprising: a
sheet member adapted to be adhered to the patient's skin in use to
provide an airtight seal around the wound, wherein the sheet member
is adapted to be spaced apart from the skin in the region of the
wound to define in use a space above the wound, and a plurality of
mutually spaced-apart flutter valves permitting one-way air, blood
and/or other fluid flow communication from the space above the
wound to the exterior of the dressing.
23. The dressing according to claim 22, wherein the dressing,
including the flutter valves, is formed from one or more sheet
materials which are of sufficient flexibility that the whole
dressing is skin-conformable and the sheet material has
substantially no rigid parts.
24. The dressing according to claim 22, wherein the sheet member is
a multilayer sheet member comprising a first layer nearest the
patient's skin in use and at least one additional layer overlying
at least a portion of the first layer on the major face thereof
directed away from the patient's skin in use, and wherein the first
layer is skin-adhesive on the major face that is directed towards
the patient's skin in use, and an aperture is provided in the first
layer, so that the first layer can surround the wound, but not
adhere to it, when the first layer is positioned on the patient's
skin to surround the wound and adheres to the patient's skin around
the wound to provide an airtight seal to the skin around the
wound.
25. The dressing according to claim 24, wherein the at least one
additional layer comprises a film layer which overlies the wound
encircling aperture above the major face of the first layer of the
sheet member that is directed away from the skin in use, and
extends radially outwardly to overlie a portion of the first layer
of the sheet member around the aperture, wherein the film layer is
sealed to the first layer of the sheet member and is provided with
a plurality of holes defining the mouths of the plurality of
flutter valves of the dressing, and wherein the flutter valves
permit one-way air, blood and/or other fluid flow communication
from the space above the wound to the exterior of the dressing.
26. The dressing according to claim 22, wherein the dressing has
two or three flutter valves.
27. The dressing according to claim 22, wherein the dressing has
four flutter valves.
28. The dressing according to claim 22, wherein the dressing has
five flutter valves.
29. The dressing according to claim 22, wherein the sheet member
includes skin-adhesive coating comprising one or more gels,
hydrocolloids, pressure-sensitive adhesives or any combination
thereof.
30. The dressing according to claim 29, wherein the skin-adhesive
coating comprises a hydrogel.
31. The dressing according to claim 30, wherein the hydrogel
comprises a hydrated polymer formed by polymerisation of one or
more monomers selected from olefinically unsaturated aliphatic or
aromatic vinyl sulphonic acids, vinyl sulphobetaines, acrylic and
methacrylic sulphonic acid esters, 2-hydroxy-3-acryloxy propyl
sulphonic acid, 2-hydroxy-3-methacryloxy propyl sulphonic acid and
2-acrylamido-2-methyl-propanesulphonic acid and salts thereof.
32. The dressing according to claim 22, further comprising a spacer
device which comprises: one or more outwardly extending projections
which in use extend in the region of the flutter valves of the
dressing and serve to space external objects away from the dressing
to prevent the flutter valves from being pressed closed by the
external objects, and apertures being present through the
projection(s) and/or between projections so that air, blood and
other fluid can pass from a space above the flutter valves to the
external atmosphere when the spacer is in place on the dressing,
when an external object is laid over the dressing and spacer.
33. A spacer device for use with a dressing comprising a sheet
member and a plurality of flutter valves, the spacer device being
adapted to be stuck to the face of the dressing that is directed
away from the patient's skin in use, comprising: one or more
outwardly extending projections which in use extend in the region
of the flutter valves of the dressing and serve to space external
objects away from the dressing to prevent the flutter valves from
being pressed closed by the external objects, and apertures being
present through the projection(s) and/or between projections so
that air, blood and other fluid can pass from a space above the
flutter valves to the external atmosphere when the spacer is in
place on the dressing, when an external object is laid over the
dressing and spacer.
34. A dressing for covering a wound of a patient, comprising: a
sheet member adapted to be adhered to the patient's skin in use to
provide an airtight seal around the wound, and one or more valves
permitting one-way air, blood and/or other fluid flow communication
from a space above the wound to the exterior of the dressing,
wherein the dressing has a threshold valve-opening overpressure of
less than about 2.2 cm H.sub.2O.
35. The dressing according to claim 34, wherein the dressing has
two, three, four or five valves.
36. The dressing according to claim 34, wherein the sheet member
includes skin-adhesive coating comprising a hydrated polymer formed
by polymerisation of one or more monomer selected from olefinically
unsaturated aliphatic or aromatic vinyl sulphonic acids, vinyl
sulphobetaines, acrylic and methacrylic sulphonic acid esters,
2-hydroxy-3-acryloxy propyl sulphonic acid,
2-hydroxy-3-methacryloxy propyl sulphonic acid,
2-acrylamido-2-methyl-propanesulphonic acid and salts thereof.
37. The dressing according to claim 34, further comprising a spacer
device which comprises: one or more outwardly extending projections
which in use extend in the region of the flutter valves of the
dressing and serve to space external objects away from the dressing
to prevent the flutter valves from being pressed closed by the
external objects, and apertures being present through the
projection(s) and/or between projections so that air, blood and
other fluid can pass from a space above the flutter valves to the
external atmosphere when the spacer is in place on the dressing,
when an external object is laid over the dressing and spacer.
38. A dressing for covering a wound of a patient suffering from a
penetrating chest wound, comprising: a sheet member adapted to be
adhered to the patient's skin in use to provide an airtight seal
around a space defined by the dressing over the wound, and at least
one valve permitting one-way air, blood and/or other fluid flow
communication from the space above the wound to the exterior of the
dressing, wherein the sheet member is adapted to be adhered to the
patient's skin in use by being provided with a skin-adhesive
coating comprising a hydrated polymer formed by polymerisation of
one or more monomer selected from olefinically unsaturated
aliphatic or aromatic vinyl sulphonic acids, vinyl sulphobetaines,
acrylic and methacrylic sulphonic acid esters, 2-hydroxy-3-acryloxy
propyl sulphonic acid, 2-hydroxy-3-methacryloxy propyl sulphonic
acid, 2-acrylamido-2-methyl-propanesulphonic acid and salts
thereof.
39. The dressing according to claim 38, wherein the dressing has
two, three, four or five valves.
40. The dressing according to claim 38, further comprising a spacer
device which comprises: one or more outwardly extending projections
which in use extend in the region of the flutter valves of the
dressing and serve to space external objects away from the dressing
to prevent the flutter valves from being pressed closed by the
external objects, and apertures being present through the
projection(s) and/or between projections so that air, blood and
other fluid can pass from a space above the flutter valves to the
external atmosphere when the spacer is in place on the dressing,
when an external object is laid over the dressing and spacer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/377,373, filed on Aug. 26, 2010, the entire
disclosure of which is incorporated herein by reference.
FIELD
[0002] The present invention relates to wound dressings,
particularly for use when an essentially one way passage of air
and/or fluid are required, as for example in the case of
penetrating wounds such as penetrating thoracic trauma. The
invention also relates to processes for the manufacture of the
compositions, and to uses of these dressings, as well as to a
spacer device for use with the dressings.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0004] The human or animal body has two lungs, each enclosed in a
separate airtight area (pleural cavity) within the chest. If an
object, for example bullet, shrapnel, knife, blast debris and/or
stick penetrates the chest wall an open chest wound results, and
allows air to enter one or both of the chest cavity area and the
pleural cavity when the person next attempts to inhale. The lung
will begin to collapse as a result of the loss of a pressure
differential between the chest cavity area or pleural cavity and
the air in the trachea, which is at outside pressure.
[0005] Any degree of collapse of either lung interferes with the
casualty's ability to breath and reduces the amount of oxygen
available for use by the body.
[0006] It is therefore important, in cases of actual or suspected
penetrating thoracic trauma, to apply a dressing that prevents the
ingress of air, through the wound in the chest wall, into the chest
cavity area or pleural space.
[0007] However, if the lung has also been punctured, then air may
also enter the pleural space via that route and if not allowed to
escape may result in an increase in pressure again resulting in a
serious impairment (life threatening) to breathing. The latter case
is known as a tension pneumothorax.
[0008] Fluids, for example blood, resulting from the trauma may
also leak into the pleural space and need to be able to escape.
[0009] Consequently any dressing applied to an actual or suspected
penetrating chest wound needs to allow the egress of air and fluid
from the pleural space but also prevent the ingress of air and
fluid.
[0010] A number of dressing constructions have been proposed to
address this issue.
[0011] In U.S. Pat. No. 5,195,977 (assigned to Lohman GmbH &
Co), the disclosure of which is incorporated herein by reference, a
wound dressing (plaster) is described which has a gas check valve
which responds to slight pressure variations. The gas check valve
is inserted in an aperture in the plaster. The skin facing side of
the plaster is coated with a pressure sensitive adhesive. The gas
check valve may be of a diaphragm, ball, plug or spring type. No
exemplification of the slight pressure variation required to
activate the valve is given. The pressure sensitive adhesive used
is described as a rubber adhesive or an acrylic adhesive.
[0012] U.S. Pat. No. 5,160,322 (assigned to Brunswick Biomedical
Technologies Inc.), the disclosure of which is incorporated herein
by reference, describes a one-way valve which permits the outward
flow of air and liquid from the chest cavity but closes against the
same flow of atmospheric air into the chest cavity. A dome
protruding from the outward facing surface of the dressing protects
the valve element.
[0013] U.S. Pat. No. 7,615,674 (Asherman), the disclosure of which
is incorporated herein by reference, describes a dressing
comprising a one way valve which is rigid to prevent obstruction of
the valve arising from turning of the patient's clothing.
[0014] U.S. Pat. No. 7,429,687 (assigned to The Seaberg Company
Inc.), the disclosure of which is incorporated herein by reference,
describes an adhesively attachable bandage comprising a valve
assembly with a rigid cover. The adhesive is preferably an
aggressive hydrogel or hydrocolloid possessing good wet tack and so
are able to adhere to damp skin. However, no description is
provided for specific examples of suitable materials.
[0015] U.S. Pat. No. 5,478,333 (Asherman), the disclosure of which
is incorporated herein by reference, describes a dressing
comprising a flexible body with adhesive on one side for attaching
the body to the skin of the patient. The centre of the body is
formed into a flexible tubular duct which projects away from the
patient. A flexible one way valve is mounted to the exterior of the
duct to allow the passage of air fluid out of the wound but
preventing air being drawn back into the wound through the
duct.
[0016] U.S. Pat. Application 2008/0234726 A1, the disclosure of
which is incorporated herein by reference, describes a chest seal
dressing with a low profile one way valve also comprising a
biocompatible adhesive. Suitable adhesives for adhering the flange
body to the patient's skin include hydro gel, acrylic, silicone
gel, silicone PSA or hydrocolloid. No specific examples are
disclosed. The passage of fluid is not described.
[0017] Due to the complexity of the valve arrangements disclosed in
the prior art the cost of these dressings is high. In addition, the
valve constructions in all of the above prior art systems have a
substantially greater thickness than the skin-adhesive portions of
the dressing in the major face to major face direction of the
dressing, and have hard or rigid portions which can press into the
wound if the patient's weight or some external force presses on the
dressing. Some of the valves (e.g., the valve of U.S. Pat. No.
5,478,333 to Asherman) can become closed permanently simply by the
patient lying awkwardly.
[0018] WO-A-2005/039465, the disclosure of which is incorporated
herein by reference, describes an attempt to solve at least some of
the above problems. The dressing described has a bandage section
which overlies the wound and is sealed to the skin around a
perimeter to enclose a space above the wound, and a single flutter
valve mouth which provides one-way fluid flow communication between
the space above the wound and the exterior environment. The valve
lies substantially in the same plane as the bandage section.
Nevertheless, the valve of this prior art is still bulky in that at
least four sheets of material (FIG. 6) are required for its
construction, and a rigid outer casing is specified as most
preferred (page 4, lines 19 to 23; page 11, lines 9 to 16).
Embodiments in which an additional fluid inlet valve is provided
for flushing-out the flutter valve are described, which is no
longer planar with the remainder of the device (FIGS. 8 to 10).
[0019] There is general concern that chest seals used for treatment
of open chest wounds can fail due to coagulation or malfunction of
the external vent and poor skin adherence. Chest seal failure may
lead to respiratory compromise or the development of a tension
pneumothorax. (Arnaud F. et al., Evaluation of chest seal
performance in a swine model: comparison of Asherman vs. Bolin
seal. Injury, 2008 September; 39(9):1082-8.). The disclosure of
this publication is incorporated herein by reference.
[0020] Dressings adapted to permit essentially one way fluid flow
away from a wound may also find use in special circumstances, such
as where a managed flow of blood from a wound, or a managed
restriction or prevention of contact between external sea water and
the wound is required.
[0021] The present invention as described below provides an
alternative, and improved dressing, over those disclosed in the
prior art. The present invention may overcome or mitigate at least
one or more problems associated with the dressings of the prior
art.
SUMMARY
[0022] In a first aspect of the present invention, there is
provided a dressing for covering a wound of a patient, for example
in the case of a penetrating chest wound to assist the patient's
breathing, comprising a sheet member adapted to be adhered to the
patient's skin in use to provide an airtight seal around the wound,
the sheet member being adapted to be spaced apart from the skin in
the region of the wound to define in use a space above the wound,
and a plurality of mutually spaced-apart flutter valves being
provided permitting one-way air, blood and/or other fluid flow
communication from the space above the wound to the exterior of the
dressing.
[0023] In a second aspect of the present invention, there is
provided a method of manufacturing a wound dressing according to
the first aspect of the present invention, comprising assembling
the parts thereof in juxtaposition suitable for forming the
dressing and securing the same together to provide the
dressing.
[0024] At least one, preferably all, of the flutter valves may
comprise one leaflet, that is: one moveable leaf which can be moved
away from a relatively fixed base surface by the flow of air and/or
liquid out of the valve, to open the valve in a one-way manner.
However, if desired a two leaflet flutter valve construction may be
employed in at least one of the valves.
[0025] The sheet member of the dressing is suitably flexible and
skin-conformable. The whole dressing, including the flutter valves,
is suitably formed solely from sheet materials which are of
sufficient flexibility that the whole dressing is skin-conformable
and has no hard or rigid parts.
[0026] It is preferred that the sheet member is a multilayer sheet
member having a first layer nearest the patient's skin in use and
at least one additional layer overlying at least a portion of the
first layer on the major face thereof directed away from the
patient's skin in use.
[0027] The first layer is preferably provided with a skin-adhesive
coating on the major face that is directed towards the patient's
skin in use, and an aperture is preferably provided in the said
first layer, preferably at the centre of the dressing, so that the
first layer can surround the wound, but not adhere to it, when the
first layer is positioned on the patient's skin to surround the
wound and adheres to the patient's skin around the wound to provide
a completely airtight seal to the skin around the wound.
[0028] For improved airtight sealing around the wound, a second
layer, formed of a sheet material that is more flexible and
optionally thinner than the material of the first layer, may be
laminated to the first layer over that portion of the major face of
the first layer that is directed away from the patient's skin in
use that surrounds the aperture, the second layer being provided
with a smaller aperture than the aperture of the first layer. When
the second layer is laminated to the first layer over the
aperture-surrounding portion of the first layer, a flange defined
by the second layer extends beyond the periphery of the aperture
and into the aperture. By providing the major face of the flange
that is directed towards the patient's skin in use with a
skin-adhesive coating, the flange can provide an additional
airtight seal to the patient's skin around the periphery of the
aperture, restricting contact between wound fluids and the
skin-adhesive coating on the skin-directed major face of the first
layer.
[0029] At least one, preferably each, of the plurality of flutter
valves may be formed by means comprising a further film layer,
preferably more flexible and thinner than the other layer or layers
of the dressing, which overlies the wound encircling aperture above
the major face of the sheet member that is directed away from the
skin in use, and extends radially outwardly thereof to overlie a
portion of the sheet member around the aperture. The further film
layer is non-adhesive both in its region that overlies over the
aperture and the region that extends radially outwardly thereof.
The further film layer is sealed airtightly to the sheet, radially
inward from the outermost border of the sheet member, around most
of the periphery of the further film layer, with a plurality of
small peripheral portions (holes) being left unsealed, said holes
defining the mouths of the plurality of flutter valves of the
dressing.
[0030] In this way, the dressing is very efficiently constructed so
as to provide an essentially planar structure without hard or rigid
valve members.
[0031] By providing a plurality of flutter valves, the need to
orientate the dressing to deliberately position a valve in a
gravitationally downward direction is eliminated or reduced. It is
preferred to have at least three, for example three, four, five or
six, valve mouths, to maximise the advantage of gravitational
draining of liquids from the dressing. The plurality of flutter
valves are provided in mutually spaced-apart relationship. A wide
range of spacing arrangements of the flutter valves is possible. It
is preferred that the flutter valves are spaced generally evenly
around the periphery of the part of the dressing defining the space
above the wound. Thus, for example, in a rectangular (including
square) dressing, four flutter valves may be provided, one on each
half-diagonal of the dressing. In a circular dressing, two, three,
four or five, for example, flutter valves may be provided, spaced
angularly evenly around the dressing. The maximum number and the
closest spacing of the flutter valves depends on the size of the
dressing, the task it is intended to perform, and the required size
of the mouth of each flutter valve.
[0032] The flutter valves provide the only route for air and/or
liquids to leave the space defined by the dressing over the wound.
Therefore, the space above the wound defined by the dressing is
said to be substantially enclosed when the dressing is in position
in use.
[0033] The dressing of the present invention therefore enables a
dressing having a low profile multiple apertured flutter valve
allowing for the one-way outward passage of air and fluid away from
the wound and being activated by a low pressure differential.
[0034] The dressing may comprise one or more additional layers if
desired. Where layers are to be sealed together over an area of
their major faces they may suitably be laminated together via an
adhesive interfacing layer, via heat sealing (welding), by
ultrasound sealing (welding), by gluing or in any other
conventional way. Where layers are to be sealed together over a
smaller region, for example along a line, they may suitably be
sealed together via an adhesive interfacing line, via linear heat
sealing (welding) or in any other conventional way.
[0035] An example of an additional layer that may be provided is a
further layer, e.g., of a woven or non-woven fabric, that may be
provided on the major face of the first layer that is directed away
from the patient's skin in use, to render the outward face of the
dressing non-adhesive. This said further layer may suitably cover
the first layer only over its part that lies radially outwardly of
the flutter valves around the wound. Preferably the outer periphery
of this further layer is coterminous with that of the first layer
(length and width)
[0036] Further, the adhesives used to laminate or seal parts of the
dressing together may be considered as layers.
[0037] Further, the skin-adhesive coating provided on the sheet
member or parts thereof may be considered as a layer.
[0038] A further example of an additional layer is a spacer device
that may be provided on the major face of the first layer that is
directed away from the patient's skin in use, to provide one or
more outwardly extending projection in the region of one or more of
the flutter valves, serving to space external objects such as
clothing, blankets, and thermal insulating sheets away from the
dressing to prevent the flutter valves from being pressed closed by
the external objects. A feature of the spacer device is that it
must maintain a fluid flow path between one or more of the flutter
valves and the external atmosphere. Therefore, if the outwardly
extending projection completely encircles an air space above the
flutter valves, or in other ways might impede air flow between one
or more of the flutter valves and the external atmosphere, the
projection is provided with through holes which allow air to pass
from the encircled region above the flutter valves to the external
atmosphere even if an external object such as clothing, a blanket
or a thermal insulating sheet is laid over the dressing.
[0039] In accordance with a further aspect of the present
invention, there is provided a spacer device for use with a
dressing according to the present invention, the spacer device
being adapted to be stuck to the face of the dressing that is
directed away from the patient's skin in use, wherein the device
comprises one or more outwardly extending projection which in use
extend in the region of one or more of the flutter valves of the
dressing and serve to space external objects such as clothing,
blankets, and thermal insulating sheets away from the dressing to
prevent the flutter valves from being pressed closed by the
external objects, apertures being present through the projection(s)
and/or between projections so that air, blood or other fluids can
pass from a space above the flutter valves to the external
atmosphere when the spacer is in place on the dressing, if an
external object such as clothing, a blanket or a thermal insulating
sheet is laid over the dressing and spacer.
[0040] A release sheet of conventional construction may also be
provided to protect the ski-adhesive parts of the dressing or the
spacer device before use.
[0041] The dressing is preferably sterile-packed in a sealed
flexible pack prior to use, in conventional manner.
[0042] The skin-adhesive coating used in the dressing of the
present invention may comprise any suitable skin-compatible
adhesive that permits an airtight seal around the wound and
prevents the dressing from becoming dislodged in normal use over a
normal residence time on the skin.
[0043] The skin-adhesive coating may suitably comprise one or more
gels (including hydrogels), hydrocolloids, pressure-sensitive
adhesives or any combination thereof. Hydrogels are preferred on
account of their non-aggressive adhesion to skin which enables the
dressing to be removed without pulling the skin or hair unduly. In
addition, hydrogels can be formed into flexible self-supporting
sheets and can be engineered to have special desirable properties.
Such properties include, for example, ability to adhere well to wet
or greasy skin, and water-unstability, by which is meant that
contact with water can actually increase the adhesion to the skin,
rather than decrease it as is typically found with conventional
adhesives. Examples of suitable hydrogel skin adhesives are
described below.
[0044] The material and thickness of the sheet member is suitably
selected to provide backing support to the skin-adhesive coating of
the dressing, depending on the inherent mechanical strength of the
skin-adhesive.
[0045] Optionally one or more of the parts of the dressing may be
made in transparent or translucent material. For example, it may
assist the carers of a patient suffering from a serious trauma
injury to be able to visualise the flows of air and/or fluids into
and out of the space above the wound enclosed by the dressing. The
portion of the dressing that covers that space may, for example, be
made from a transparent or translucent material for that
reason.
[0046] The dressing may be adapted for human or animal use.
[0047] The dressing of the present invention may be connected to
one or more fluid collection bag, to collect fluid that may emerge
via the flutter valves. In one embodiment, a fluid collection bag
for use with the present invention may comprise a flexible
receptacle having a mouth and a flange disposed around the mouth,
the flange being coated with an adhesive so the flange may adhere
to the outwardly directed surface of the dressing of the present
invention in use, encircling at least one of the flutter valve
mouths, preferably at least the gravitationally lowest one or more
or the flutter valve mouths, and most preferably not all of the
flutter valve mouths simultaneously. The assembly of the dressing
and the collection bag thereby provides a system which contains all
or most of the liquids expelled from the wound, while still
permitting the one-way airflow communication from the space above
the wound to the exterior of the dressing.
[0048] We have found that the chest seal dressings have a
surprisingly low threshold valve-opening overpressure, by which is
meant the air overpressure between the skin-directed major face of
the dressing and the opposite major face of the dressing (the air
at said opposite major face is normally at atmospheric pressure) at
which the one-way valve system of the dressing opens to permit air
and other fluid to flow out through the dressing. Moreover, the low
threshold valve-opening overpressure of the chest seal dressings is
remarkably constant and well-maintained across different samples of
dressings according to the present invention, different test or
operation procedures, different storage ages of dressings and
different lengths of use of dressings. Moreover, these advantages
are maintained over a wide range of embodiments of materials and
construction details, typical details of which are given
herein.
[0049] For example, we have found that the chest seal dressings
according to the present invention consistently have a threshold
valve-opening overpressure of less than about 2.2 cm H.sub.2O, more
preferably less than about 1.5 cm H.sub.2O, and more preferably
less than about 1 cm H.sub.2O, as measured using the test method
described in Example 2 below.
[0050] Chest seal dressings having such a low threshold
valve-opening overpressure are not available in the prior art.
[0051] Therefore, according to a further aspect of the present
invention, there is provided a dressing for covering a wound of a
patient, for example in the case of a penetrating chest wound to
assist the patient's breathing, comprising a sheet member adapted
to be adhered to the patient's skin in use to provide an airtight
seal around the wound, and one or more valve being provided
permitting one-way air, blood and/or other fluid flow communication
from a space above the wound to the exterior of the dressing,
wherein the dressing has a threshold valve-opening overpressure of
less than about 2.2 cm H.sub.2O, for example as measured using the
test method described in Example 2 below.
[0052] The dressing defined in the preceding paragraph preferably
has a threshold valve-opening overpressure of less about 1.5 cm
H.sub.2O, and more preferably less than about 1 cm H.sub.2O.
[0053] The dressing is preferably a chest seal dressing, more
preferably a dressing as described according to any one or more of
the other aspects or embodiments of the present invention.
[0054] The low threshold valve-opening overpressure of the dressing
described and claimed herein is preferably constant within the
defined low range across a range of individual dressings
manufactured in the same or different batches, for example across
at least 100 different dressings.
[0055] The low threshold valve-opening overpressure of the dressing
described and claimed herein is preferably constant within the
defined low range across a range of different storage ages of
individual dressings, for example across dressings stored for
between 5 days and 800 days at room temperature and pressure. In
particular, the dressings of the present invention maintain their
performance even when stored in a distorted condition or under
pressure from other articles. This contrasts with the prior art
dressings that incorporate valves, where distortion or pressure can
cause the valve parts to distort or self-seal or self-open, so that
the valve becomes inoperable for its medical purpose.
DETAILED DESCRIPTION
[0056] Constructions of the Dressing
[0057] In one embodiment the dressing as provided ready for use may
comprise four superimposed layers.
[0058] In this embodiment a conventional release sheet constitutes
a bottom layer, not counted in the four.
[0059] Overlain over the total upper surface of the bottom layer,
and provided with an aperture--preferably a central aperture--where
the wound will be in use, is a first layer of the dressing itself,
constituted by a skin-adhesive layer.
[0060] Overlain over the total upper surface of the skin-adhesive
layer, and also provided with a corresponding aperture where the
wound will be in use, is a layer of a backing material for the
dressing (second layer) such as a woven or non-woven fabric, which
provides mechanical support to the skin-adhesive layer and prevents
the upper surface of the skin-adhesive layer from sticking to
external objects in use. The backing material is suitably chosen
for strength and lightness, as well as flexibility and
skin-conformability, and to provide a pleasant touch sensation when
touching the external surface of the dressing directed away from
the skin.
[0061] Overlain over the upper surface of the backing material
layer (but preferably not over the total area of the backing
material) is a third layer which provides an anchor for sealing the
fourth layer (described below) that forms the moveable parts of the
flutter valves. The third layer of the dressing is provided with an
aperture generally corresponding to the apertures of the first and
second layers where the wound will be in use. Preferably, however,
the aperture in the third layer is smaller than the aperture in the
first and second layers described previously, so that a flange of
the material of the third layer extends into the aperture of the
first and second layers around its periphery, for example by a
distance of about 0.2 to about 1 cm, preferably about 0.5 cm. By
selecting the material of the third layer to be of suitable
flexibility, and providing a suitable skin-adhesive coating on the
underside of the flange, the flange can in use stick to the skin
surrounding the wound and thereby enhance the air-tight seal around
the wound as well as restricting direct contact between blood and
other wound fluids and the skin-adhesive of the first layer.
[0062] The fourth layer is overlain on the upper surface of the
third layer (either over the total area of the third layer or a
portion thereof), and is formed of a thin film having sufficient
flexibility to serve as the moveable portions of the plurality of
flutter valves. This layer has no aperture corresponding to the
apertures of the first to third layers mentioned above, but instead
a plurality of holes near its periphery, these holes being
dimensioned and arranged to serve in use as the mouths of the
flutter valves. The fourth layer is non-adhesive on both major
faces, and is sealed to the upper surface to the third layer in a
seal line around its periphery, ensuring that the holes are free to
open and close in use in flutter valve manner, cooperating with the
underlying portion of the upper surface of the third layer. The
holes of the fourth layer are preferably cut or punched in the
material of the fourth layer, and shaped to have minimal sharp
corners of other points where the material can become stressed
during working of the flutter valves. The holes are most preferably
generally circular, elliptical or lenticular in shape over at least
the portion of their edges that is at risk of highest degrees of
stress in use.
[0063] The first layer and fourth layer, in use, are typically in
fluid communication with the wound. At least part of one surface,
optionally all of one surface, of the first layer may be exposed
for contacting a wound. Optionally, one or more further apertured
layers and/or materials may be disposed between the wound and the
first and/or fourth layer such that portions of the first layer
still contact the skin. Examples of such additional materials
include nets and nets with antimicrobial properties.
[0064] The layers are suitably secured together by appropriate
conventional means, for example gluing, melt-welding, heat welding,
ultrasound welding, or any combination thereof. Of course, where a
layer has its own adhesiveness, it may be adhered directly to an
adjacent layer.
[0065] Treatments
[0066] The dressing of the present invention may suitably be used
for dressing a penetrating chest wound and particularly for the
prevention of tension pneumothorax.
[0067] Manufacture
[0068] The present invention also provides a method of
manufacturing of the dressing according to the first aspect of the
invention.
[0069] The method, which constitutes a third aspect of the present
invention, comprises assembling the parts thereof in juxtaposition
suitable for forming the dressing and securing the same together to
provide the dressing, for example using conventional securing
means.
[0070] For example the embodiment of the invention described above
may be manufactured by assembling and adhering together the first
and second layers, optionally with one or more further layers
and/or materials disposed between the layers, to form a multilayer
composite, and subsequently cutting or punching out the gap where
the wound will be accommodated in use. Then the third and fourth
layers, optionally with one or more further layers and/or materials
disposed between the layers and/or between the third and second
layers, may be assembled and secured in place. The assembling may
comprise forming one or more of the first, second and third layers,
in situ, such that, once formed, the layer is adhered to one or
more of the other layers in the dressing.
[0071] Physical Properties of the Dressing
[0072] The dressing is preferably flexible, preferably skin
conformable. The dressing is preferably adapted to keeping a wound
moist
[0073] Skin-Adhesive
[0074] The skin-adhesive layer (coating) and optionally any backing
layer to support it is/are preferably compressible.
[0075] The skin-adhesive material is preferably a self-supporting
material.
[0076] The skin-adhesive layer, in use, preferably can removably
adhere to skin and/or a wound.
[0077] The skin-adhesive is preferably a viscoelastic material.
Viscoelastic materials are known to the skilled person. A
viscoelastic material typically has one or more of the following
properties: (i) hysteresis in the material's stress-strain curve;
(ii) stress relaxation occurs in the material: step constant strain
causes decreasing stress; and (iii) creep occurs in the material:
step constant stress causes increasing strain. A viscoelastic
material typically loses energy when a load is applied and then
removed. The first layer will typically comprise two opposing
surfaces, which can be termed first and second surfaces, one of
which may be exposed at least in part for contacting a wound.
[0078] The skin-adhesive material suitably comprises a gel,
preferably a hydrogel. A "gel" includes, but is not limited to, a
self-supporting, flexible substance, optionally comprising one or
more polymers. A gel may comprise water. The first material is
preferably a viscoelastic hydrogel. The first layer may consist
essentially of or consist of a gel, for example a hydrogel, and any
water contained therein. It may also comprise a scrim (supportive
mesh) within the gel "Consist essentially of" in this context
includes, but is not limited to, the first layer comprising about
25 wt % or less, preferably about 20 wt % or less, of components
other than the gel and any water it may contain.
[0079] Other Optional Features, e.g., Other Layers, of the
Dressing
[0080] The second layer may comprise two opposed major faces, one
or both of which may have a pressure sensitive adhesive thereon,
for adhesion to one or more of the other layers in the composition,
for example the first and third layers. In an embodiment of the
invention the second layer is preferably permeable to moisture
vapour. In a further embodiment of the invention the second layer
is preferably a non-woven fibre-based fabric. The upper surface of
the second layer material may, in use, constitute at least part of
outermost surface of the dressing.
[0081] The third layer provides a backing layer to the first layer
to cover the adhesive first layer and to provide a base for the
attachment of the flutter valve assembly to the first layer. The
third layer will typically comprise two opposed major faces, one of
which, in use, will face the wound and the other of which will face
away from the wound. The wound-facing face of the third layer may
have disposed thereon a pressure sensitive adhesive for adhesion to
other layers of the composite, for example the second layer. The
pressure sensitive adhesive may form a continuous or discontinuous
coating on the skin-facing face of the third layer. Preferably, the
face of the third layer facing away from the wound does not have an
adhesive thereon. In am embodiment of the invention the third layer
may extend beyond the margins of the aperture (gap) in the first
and/or second layer to minimize any contact between the adhesive
first layer and the outermost layer which provides the moving parts
of the flutter valves, namely a seal on inspiration and may open on
expiration during the breathing cycles.
[0082] An optional fifth layer may be present to bond the third and
fourth layers and may comprise a double-sided adhesive. In the
absence of the fifth layer the fourth layer may be directly bonded
to the third layer by means of an adhesive (complete or partial
covering) on the non-wound-facing face of the third layer, or an
adhesive may be partially coated around the perimeter of the
wound-facing face of the fourth layer. Other means of adhering the
third layer to the fourth layer will be evident to those skilled in
the art and include but not limited to welding by heat or
ultrasonic means.
[0083] The fourth layer comprises a film material possessing
sufficient strength and flexibility to seal the preferably central
located apertures in all the other layers of the dressing during
inspiration and to move outwards during expiration if the pressure
in the inter pleural cavity is too high. In a preferred embodiment
there are more than one apertures in the fourth layer located such
that there is no direct overlap with any of the apertures present
in the other layers of the dressing. The apertures in the fourth
layer are of a sufficiently large dimension to permit a reasonable
flow of fluid (if present) away from the body during expiration but
not of dimension sufficiently large to prevent the dressing from
acting as a seal during inspiration.
[0084] Release liner layers may be applied to the exposed upper and
lower surface of the multilayer dressing to facilitate ease of
handling and packaging, as previously mentioned.
[0085] In one embodiment, the first layer may be thicker than the
second layer.
[0086] In one embodiment, the second layer may be thicker than the
third layer.
[0087] The first layer may suitably have a thickness of about 0.1
mm or more, more preferably about 0.3 mm or more, more preferably
about 0.5 mm or more and even more preferably about 1 mm or more.
The aperture (gap) is preferably centrally located with respect to
the area of the layer and maybe of any shape including but not
limited to a circle, square, diamond, rectangle or oval. The
aperture has an area greater than about 20 mm.sup.2 , preferably
greater than about 50 mm.sup.2 and preferably greater than about
100 mm.sup.2.
[0088] The second layer may have a thickness of about 0.1 mm or
more, more preferably about 0.2 mm or more, and even more
preferably about 0.4 mm or more. The second layer preferably has a
thickness of about 2 mm or less, more preferably about 1 mm or
less. The aperture (gap) is preferably centrally located with
respect to the area of the layer and maybe of any shape including
but not limited to a circle, square, diamond, rectangle or oval.
Preferably the aperture is of the same shape and dimension and
orientation as the aperture in the first layer. The aperture has an
area greater than about 20 mm.sup.2, preferably greater than about
50 mm.sup.2 and preferably greater than about 100 mm.sup.2.
[0089] The third layer, including any optional adhesive layer which
may be disposed on a surface of the third layer, may have a
thickness of about 0.03 mm or more, more preferably about 0.07 mm
or more and even more preferably about 0.1 mm or more. The aperture
(gap) is preferably centrally located with respect to the area of
the layer and maybe of any shape including but not limited to a
circle, square, diamond, rectangle or oval. The aperture has an
area greater than about 20 mm.sup.2, preferably greater than about
50 mm.sup.2 and preferably greater than about 100 mm.sup.2.
[0090] In a preferred embodiment the area of the aperture in the
third layer is less than the area of the apertures in the first or
second layers such that the third layer overlaps the margins of the
aperture formed by the first and second layers. The outer perimeter
of the third layer is preferably less than that of the first and
second layers.
[0091] The fourth layer may have a thickness of about 0.01 mm or
more, more preferably about 0.015 mm or more, more preferably about
0.02 mm or more and preferably less than about 0.5 mm. Preferably
the fourth layer has a more than one aperture. Each aperture is
preferably located off centre with respect to the area of the layer
and maybe of any shape including but not limited to a circle,
square, diamond, rectangle or oval. The area of the individual
apertures in the fourth layer is preferably greater than about 10
mm.sup.2, more preferably greater than about 15 mm.sup.2 and even
more preferably greater than about 18 mm.sup.2 but preferably less
than about 40 mm.sup.2. The sizes of the apertures in the fourth
layer reflect the internal areas of commonly used chest drain
tubes.
[0092] The optional fifth layer described above, when present, may
have a thickness of about 0.02 mm or more, more preferably about
0.05 mm or more, more preferably about 0.1 mm or more and
preferably less than about 0.5 mm. The outer perimeter of the fifth
layer is preferably less that that of the first and second layers.
The aperture in the fifth layer suitably has an area greater that
that of the first or second layers such that the first and second
layers extend beyond the margin of the aperture in the fifth layer
when the layers are superimposed in the dressing.
[0093] Spacer Device
[0094] The spacer device is suitably constructed in the form of a
complete or partial ring of rigid sheet material having a
face-to-face thickness suitably up to about 2 cm, preferably about
0.2 to about 0.5 cm, for example about 0.25 cm, with an adhesive
provided on one major face so that the spacer can be stuck to the
face of the dressing that is directed away from the patient's skin
in use. The size of the ring is suitably such as to encircle all
the flutter valves of the dressing. The ring may be any suitable
shape, and we have found that a shape corresponding generally to
the shape of the dressing, but a little smaller than the outside
limits of the dressing, is suitable. The spacer can, for example,
have through-holes passing between the radially inward and radially
outward sides of the ring, which allow air to pass from the
encircled region above the flutter valves to the external
atmosphere when the spacer is in place on the dressing, when an
external object such as clothing, a blanket or a thermal insulating
sheet is laid over the dressing and spacer. For example, the spacer
device may be formed of a corrugated plastic sheet material cut or
pressed into the desired shape (e.g., a ring) and provided with an
adhesive layer on one face.
[0095] Gels
[0096] The skin-adhesive, e.g., comprising the first layer,
preferably comprises a hydrocolloid, a hydrogel or other
viscoelastic gel.
[0097] The gel may comprise, consist essentially of or consist of a
cross-linked hydrophilic polymer of a hydrophilic monomer and
optionally one or more comonomers, together with water and/or one
or more organic plasticiser, and optionally together with one or
more additives selected from surfactants, polymers, pH regulators,
electrolytes, chloride sources, bioactive compounds (including
antimicrobial agents) and mixtures thereof, with less than about
30% by weight of other additives.
[0098] The skin-adhesive may comprise a hydrocolloid. The
hydrocolloid may be selected from sodium carboxymethylcellulose,
pectin, gelatine, guar gum, locust bean gum, karaya gum, and
mixtures thereof.
[0099] The skin-adhesive may alternatively comprise a pressure
sensitive acrylic adhesive.
[0100] Preferably, the skin-adhesive comprises a hydrogel. The
expression "hydrogel" and like expressions, used herein, are not to
be considered as limited to gels which contain water, but extend
generally to all hydrophilic gels, including those containing
organic non-polymeric components in the absence of water. The gel
forming agent may, for example, be selected from natural
hydrophilic polymers, synthetic hydrophilic polymers,
hydrocolloids, gelling hydrophilic biopolymers and all combinations
thereof.
[0101] Hydrogels are, generally speaking, hydrophilic polymers
characterized by their hydrophilicity (i.e., capacity to absorb
large amounts of fluid such as wound exudate) and insolubility in
water: i.e., they are capable of swelling in water while generally
preserving their shape.
[0102] The hydrophilicity is generally due to groups such as
hydroxyl, carboxy, carboxamido, and esters, among others. On
contact with water, the hydrogel assumes a swollen hydrated state
that results from a balance between the dispersing forces acting on
hydrated chains and cohesive forces that do not prevent the
penetration of water into the polymer network. The cohesive forces
are most often the result of crosslinking, but may result from
electrostatic, hydrophobic or dipole-dipole interactions.
[0103] Useful classes of hydrogels in the present invention include
those polymers and copolymers derived from acrylic and methacrylic
acid ester, including hydroxyalkyl (meth)acrylates,
2-(N,N-dimethylamino)ethyl methacylate, methacryloyloxyalkyl
sulfonates (generally crosslinked with diacrylate or
divinylbenzene), polymers and copolymers of substituted and
unsubstituted acrylamides, polymers and copolymers of
N-vinylpyrrolidinone, and polyelectrolyte complexes. Hydrogels are
described in greater detail in Hydrogels, Kirk-Othmer Encyclopedia
of Chemical Technology, 4th Edition, vol. 7, pp. 783-807, John
Wiley and Sons, New York, the contents of which are incorporated
herein by reference.
[0104] The term "hydrogel" is used herein regardless of the state
of hydration.
[0105] The hydrogel used in connection with the present invention
will suitably comprise a substantially water-insoluble,
crosslinked, partially neutralized, gel-forming polymer material.
Such hydrogel materials can be prepared from polymerisable,
unsaturated, acid- and ester-containing monomers. Examples of such
monomers are described in more detail below.
[0106] The hydrogel used in the present invention preferably
comprises a plasticised three-dimensional matrix of cross-linked
polymer molecules, and has sufficient structural integrity to be
self-supporting even at very high levels of internal water content
(e.g., a water content of at least 20%, optionally 50%, by weight)
with sufficient flexibility to conform to the surface contours of
mammalian skin or other surface with which it is in contact.
[0107] The hydrogel generally comprises, in addition to the
cross-linked polymeric network, an aqueous or non-aqueous
plasticising medium including an organic plasticiser. This
plasticising medium is preferably present in the same precursor
solution as the monomer(s).
[0108] The precursor liquid can comprise a solution of the
gel-forming polymer in a relatively volatile solvent, whereby the
hydrogel is deposited as a residue on evaporation of the solvent,
or--more preferably--the precursor liquid will comprise a solution
of the monomer(s), cross-linking agent, plasticiser, and optionally
water and other ingredients as desired, whereby the hydrogel is
formed by a curing reaction performed on the precursor liquid after
application to the substrate to which the hydrogel is to be
applied.
[0109] In the following discussion, the second form of precursor
solution and application protocol (in situ polymerisation of the
hydrogel) will be discussed. The solvent deposition method carried
out on a pre-formed gel-forming polymer is well known and the
details of that procedure do not need to be reproduced here.
[0110] The polymerisation reaction is preferably a free-radical
polymerisation with cross-linking, which may for example be induced
by light, heat, radiation (e.g., ionising radiation), or redox
catalysts, as is well known.
[0111] For example, the free radical polymerisation may be
initiated in known manner by light (photoinitiation), particularly
ultraviolet light (UV photoinitiation); heat (thermal initiation);
electron beam (e-beam initiation); ionising radiation, particularly
gamma radiation (gamma initiation); non-ionising radiation,
particularly microwave radiation (microwave initiation); or any
combination thereof. The precursor solution may include appropriate
substances (initiators), at appropriate levels, e.g., up to about
5% by weight, more particularly between about 0.002% and about 2%
by weight, which serve to assist the polymerisation and its
initiation, in generally known manner.
[0112] Preferred photoinitiators include any of the following
either alone or in combination: Type I-hydroxy-ketones and
benzilidimethyl-ketals e.g., Irgacure 651. These are believed on
irradiation to form benzoyl radicals that initiate polymerisation.
Photoinitiators of this type that are preferred are those that do
not carry substituents in the para position of the aromatic ring. A
particularly preferred photoinitiator is 1-hydroxycyclohexyl phenyl
ketone; for example, as marketed under the trade name Irgacure 184
by Ciba Speciality Chemicals. Also preferred are Daracur 1173
(2-hydroxy-2-propyl phenyl ketone) and mixtures of Irgacure 184 and
Daracur 1173. Photo-polymerisation is particularly suitable, and
may be achieved using light, optionally together with other
initiators, such as heat and/or ionizing radiation. Photoinitiation
will usually be applied by subjecting the pre-gel reaction mixture
containing an appropriate photoinitiation agent to ultraviolet (UV)
light. The incident UV intensity, at a wavelength in the range from
240 to 420 nm, is typically greater than about 10 mW/cm.sup.2. The
processing will generally be carried out in a controlled manner
involving a precise predetermined sequence of mixing and thermal
treatment or history. The UV irradiation time scale should ideally
be less than 60 seconds, and preferably less than 10 seconds to
form a gel with better than 95% conversion of the monomers. Those
skilled in the art will appreciate that the extent of irradiation
will be dependent on a number of factors, including the UV
intensity, the type of UV source used, the photoinitiator quantum
yield, the amount of monomer(s) present, the nature of the
monomer(s) present and the presence of polymerisation inhibitor. In
one preferred embodiment, (on the one hand) the precursor solution
in contact with the substrate to which it is to be applied and (on
the other hand) the source of the polymerisation initiator (e.g.,
the radiation source) may move relative to one another for the
polymerisation step. In this way, a relatively large amount of
polymerisable material can be polymerised in one procedure, more
than could be handled in a static system. This moving, or
continuous, production system is preferred. After completion of the
polymerisation, the product is preferably sterilised in
conventional manner. The sterile composite may be used immediately,
e.g., to provide a skin-adhesive layer in an article, or a top
release layer may be applied to the composite for storage and
transportation of the composite. If desired, certain ingredients of
the hydrogel may be added after the polymerisation and optional
cross-linking reaction. However, it is generally preferred that
substantially all of the final ingredients of the hydrogel are
present in the precursor solution, and that--apart from minor
conventional conditioning or, in some cases, subsequent
modifications caused by the sterilisation procedure--substantially
no chemical modification of the hydrogel takes place after
completion of the polymerisation reaction.
[0113] Monomers
[0114] The gel preferably comprises a polymer having pendant
sulphonyl groups, and optionally pendant carboxylic acid groups in
acid or salt form. The hydrogel used in the present invention
suitably may comprise a substantially water-insoluble, crosslinked,
at least partially neutralized, gel-forming polymer material having
the pendant sulphonyl groups, and optionally pendant carboxylic
groups, in acid or salt form at least at its wound-contacting
surface. The hydrogel polymer materials can be prepared from
polymerizable, unsaturated, acid- and ester-containing monomers.
The hydrogel polymer may be present at the wound-contacting surface
of the composition and contain pendant sulphonyl groups, in acid or
salt form, and optionally carboxylic groups in acid or salt form.
Thus, such monomers include the olefinically unsaturated acids,
esters and anhydrides which contain at least one carbon to carbon
olefinic double bond. More specifically, these monomers can be
selected from olefinically unsaturated carboxylic acids, carboxylic
esters, carboxylic acid anhydrides; olefinically unsaturated
sulphonic acids; and mixtures thereof.
[0115] Olefinically unsaturated carboxylic acid, carboxylic acid
ester and carboxylic acid anhydride monomers include the acrylic
acids typified by acrylic acid itself, methacrylic acid, ethacrylic
acid, .alpha.-chloroacrylic acid, .alpha.-cyano-acrylic acid,
.beta.-methyl-acrylic acid (crotonic acid), .alpha.-phenyl acrylic
acid, .beta.-acryloxy-propionic acid, sorbic acid,
.alpha.-chloro-sorbic acid, angelic acid, cinnamic acid,
4-chloro-cinnamic acid, .beta.-styryl-acrylic acid
(1-carboxy-4-phenyl-1,3-butadiene), itaconic acid, citraconic acid,
mesaconic acid, glutaconic acid, aconitic acid, maleic acid,
fumaric acid, tricarboxy-ethylene and maleic acid anhydride and
salts (e.g., alkali metal salts such as sodium, potassium and
lithium salts) thereof. For forming any polymer to be present at
the lesion-contacting surface of the composition, the monomer or
monomer mixture will include a monomer containing pendant sulphonyl
groups, e.g., --SO.sub.3 in acid or salt form.
[0116] Olefinically unsaturated sulphonic acid monomers include
aliphatic or aromatic vinyl sulphonic acids such as vinylsulphonic
acid, allylsulphonic acid, vinyltoluenesulphonic acid and styrene
sulphonic acid; vinyl sulphobetaines such as SPDA (1-propanaminium
N,N-dimethyl-N-[2-[(1-oxo-2-propenyl)oxy]-3-sulfo hydroxide, inner
salt (available from Raschig); acrylic and methacrylic sulphonic
acid such as sulphoethyl acrylate, sulphoethyl methacrylate,
sulphopropyl acrylate, sulphopropyl methacrylate,
2-hydroxy-3-acryloxy propyl sulphonic acid,
2-hydroxy-3-methacryloxy propyl sulphonic acid and
2-acrylamido-2-methyl-propanesulphonic acid and salts (e.g.,
ammonium or alkali metal salts, such as sodium, potassium and
lithium salts, or alkaline earth metal salts, such as calcium or
magnesium) thereof.
[0117] The monomers may suitably be used in admixture with each
other or with other monomers. In one particularly useful embodiment
of the invention, a monomer which has a first counter-cation
associated with it may be used in admixture with one or more
monomer which has/have one or more second/further counter-cation(s)
associated with it/them. The first counter-cation and the
second/further counter cation may be the same or different. The
monomers in their anionic form (i.e., disregarding the
counter-cation) may be the same or different. In this way, the
proportions of different cations (e.g., alkali metal ions such as
sodium or potassium, or ammonium ions) can be finely controlled in
the resultant polymer (homopolymer or copolymer). The particular
weight ratios of one monomer to the or each other monomer can be
selected within wide limits by those skilled in the art, depending
on the desired properties of the resultant hydrogel polymer.
[0118] Further examples of suitable monomers for use in the present
invention include: a polyalkylene glycol acrylate or a substituted
derivative thereof; a polyalkylene glycol methacrylate or a
substituted derivative thereof; acrylic acid and salts thereof
(e.g., alkali metal salts such as sodium, potassium and lithium
salts); 2-acrylamido-2-methyl-propanesulphonic acid and salts
thereof (e.g., ammonium or alkali metal salts, such as sodium,
potassium and lithium salts, or alkaline earth metal salts, such as
calcium or magnesium); acrylic acid (3-sulphopropyl) ester or a
substituted derivative thereof or a salt thereof (e.g., an alkali
metal salt such as sodium, potassium or lithium salt); diacetone
acrylamide (N-1,1-dimethyl-3-oxobutyl-acrylamide); a vinyl lactam
(e.g., N-vinyl pyrrolidone or a substituted derivative thereof); an
optionally substituted N-alkylated acrylamide such as hydroxyethyl
acrylamide; and an optionally substituted N,N-dialkylated
acrylamide; and/or N-acryloyl morpholine or a substituted
derivative thereof. For forming any polymer of the hydrogel, which
may in use contact the wound, the monomer or monomer mixture may
include a monomer containing pendant sulphonyl groups, e.g.,
--SO3.sup.- in acid or salt form, and optionally carboxylic groups
in acid or salt form.
[0119] Particularly preferred monomers include: the sodium salt of
2-acrylamido-2-methylpropane sulphonic acid, commonly known as
NaAMPS, which is available commercially at present from Lubrizol as
either a 50% aqueous solution (reference code LZ2405) or a 58%
aqueous solution (reference code LZ2405A); acrylic acid
(3-sulphopropyl) ester potassium salt, commonly known as SPA or
SPAK (SPA or SPAK is available commercially in the form of a pure
solid from Raschig); acrylic acid (3-sulphopropyl) ester sodium
salt, commonly known as SPANa (SPANa is available in the form of a
pure solid from Raschig); N-acryloyl morpholine; and hydroxyethyl
acrylamide.
[0120] The above monomers and monomer types may optionally include
substituent groups. Optional substituents of the monomers used to
prepare the hydrogels used in the present invention may preferably
be selected from substituents which are known in the art or are
reasonably expected to provide polymerisable monomers which form
hydrogel polymers having the properties necessary for the present
invention. Suitable substituents include, for example, lower alkyl
(e.g., C.sub.1 to C.sub.10, optionally C.sub.1 to C.sub.5),
hydroxy, halo and amino groups.
[0121] Cross-Linking Agents
[0122] Conventional cross-linking agents are suitably used to
provide the necessary mechanical stability and to control the
adhesive properties of the hydrogel. The amount of cross-linking
agent required will be readily apparent to those skilled in the art
such as from about 0.01% to about 0.5%, particularly from about
0.05% to about 0.4%, most particularly from about 0.08% to about
0.3%, by weight of the total polymerisation reaction mixture.
Typical cross-linkers include tripropylene glycol diacrylate,
ethylene glycol dimethacrylate, triacrylate, polyethylene glycol
diacrylate (polyethylene glycol (PEG) molecular weight between
about 100 and about 4000, for example PEG400 or PEG600), and
methylene bis acrylamide.
[0123] Organic Plasticisers
[0124] The hydrogel and/or its pre-gel may comprise one or more
organic plasticisers. The one or more organic plasticisers may
suitably comprise any of the following either alone or in
combination: at least one polyhydric alcohol (such as glycerol,
polyethylene glycol, or sorbitol), at least one ester derived
therefrom, at least one polymeric alcohol (such as polyethylene
oxide) and/or at least one mono- or poly-alkylated derivative of a
polyhydric or polymeric alcohol (such as alkylated polyethylene
glycol). Glycerol is the preferred plasticiser. An alternative
preferred plasticiser is the ester derived from boric acid and
glycerol. When present, the organic plasticiser may comprise up to
about 45% by weight of the hydrogel composition.
[0125] Surfactants
[0126] Any compatible surfactant may optionally be used as an
additional ingredient of the hydrogel composition. Surfactants can
lower the surface tension of the mixture before polymerisation and
thus aid processing. The surfactant or surfactants may be
non-ionic, anionic, zwitterionic or cationic, alone or in any
mixture or combination. The surfactant may itself be reactive,
i.e., capable of participating in the hydrogel-forming reaction.
The total amount of surfactant, if present, is suitably up to about
10% by weight of the hydrogel composition, preferably from about
0.05% to about 4% by weight.
[0127] In a preferred embodiment of the invention the surfactant
comprises at least one propylene oxide/ethylene oxide block
copolymer, for example such as that supplied by BASF Plc under the
trade name Pluronic P65 or L64.
[0128] Other Additives
[0129] The hydrogel in the composite of the present invention may
include one or more additional ingredients, which may be added to
the pre-polymerisation mixture or the polymerised product, at the
choice of the skilled worker. Such additional ingredients are
selected from additives known in the art, including, for example,
water, organic plasticisers, surfactants, polymeric material
(hydrophobic or hydrophilic in nature, including proteins, enzymes,
naturally occurring polymers and gums), synthetic polymers with and
without--pendant carboxylic acids, electrolytes, pH regulators,
colourants, chloride sources, bioactive compounds and mixtures
thereof. The polymers can be natural polymers (e.g., xanthan gum),
synthetic polymers (e.g., polyoxypropylene-polyoxyethylene block
copolymer or poly-(methyl vinyl ether alt maleic anhydride)), or
any combination thereof. By "bioactive compounds" we mean any
compound or mixture included within the hydrogel for some effect it
has on living systems, whether the living system be bacteria or
other microorganisms or higher animals such as the patient.
Bioactive compounds that may be mentioned include, for example,
pharmaceutically active compounds, antimicrobial agents, antiseptic
agents, antibiotics and any combination thereof. Antimicrobial
agents may, for example, include: sources of oxygen and/or iodine
(e.g., hydrogen peroxide or a source thereof and/or an iodide salt
such as potassium iodide) (see, for example Bioxzyme technology,
for example in The Sunday Telegraph (UK) 26 January 2003 or the
discussion of the Oxyzyme system at
www.wounds-uk.com/posterabstracts2003.pdf); honey (e.g., active
Manuka honey); antimicrobial metals, metal ions and salts, such as,
for example, silver-containing antimicrobial agents (e.g.,
colloidal silver, silver oxide, silver nitrate, silver
thiosulphate, silver sulphadiazine, or any combination thereof); or
any combination thereof.
[0130] In the Bioxzyme system, a dressing comprises two hydrogels.
One contains glucose based antibacterial compounds and the other
contains enzymes that convert the glucose into hydrogen peroxide.
When these are exposed to air and contacted together at a wound
site, the enzyme-containing gel being adjacent the skin and the
glucose-containing gel overlying the enzyme-containing gel, a low
level steady flow of hydrogen peroxide is produced, which inhibits
anaerobic bacteria. This antibacterial effect can be enhanced by
the inclusion of a very low level of iodide (less than about 0.04%)
in the hydrogel. The hydrogen peroxide and the iodide react to
produce iodine, a potent antimicrobial agent.
[0131] Hydrogels incorporating antimicrobial agents may, for
example, be active against such organisms as Staphylococcus aureus
and Pseudomonas aeruginosa.
[0132] Additional polymer(s), typically rheology modifying
polymer(s), may be incorporated into the polymerisation reaction
mixture at levels typically up to about 10% by weight of total
polymerisation reaction mixture, e.g., from about 0.2% to about 10%
by weight. Such polymer(s) may include polyacrylamide, poly-NaAMPS,
polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) or
carboxymethyl cellulose.
[0133] The hydrogel preferably used in the present invention may
consists essentially of a cross-linked hydrophilic polymer of a
hydrophilic monomer and optionally one or more comonomer, together
with water and/or one or more organic plasticiser, and optionally
together with one or more additives selected from surfactants,
polymers, pH regulators, electrolytes, chloride sources, bioactive
compounds and mixtures thereof, with less than about 30%,
optionally less than about 20%, optionally less than 10% by weight
of other additives.
[0134] The water activity, which is related to the osmolarity and
the ionic strength of the precursor solution (as measured, for
example, by a chilled mirror dewpoint meter, Aqualab T3) is
preferably between 0.05 and 0.99, more preferably between, 0.2 and
0.99, even more preferably between 0.3 and 0.98 and even more
preferably between 0.4 and 0.8. The higher the ionic strength,
reflected in a lower water activity, the lesser the swelling of the
fibre structure. The ionic strength of the precursor solution can
therefore be used to optimise the hydrogel composite
properties.
[0135] For further details of the hydrogel material for use in the
present invention, and its preparation, please refer to the
following publications: PCT Patent Applications Nos. WO-97/24149,
WO-97/34947, WO-00/06214, WO-00/06215, WO-00/07638, WO-00/46319,
WO-00/65143, WO-01/96422 and WO 2007/007155, the disclosures of
which are incorporated herein by reference.
[0136] Optional Components
[0137] One or more porous sheets, for example a scrim, may be
disposed within or on a surface of one or more of the layers,
preferably the first layer, and preferably within or on a surface
of the gel material, preferably a hydrogel material. A scrim
includes, but is not limited to, porous sheets comprising materials
selected from woven, non-woven and net materials. Such a scrim
material may be formed of a material that is natural in origin,
synthetic in origin, or partly natural and partly synthetic. The
scrim may suitably be in the form of a net or a woven or non-woven
fabric. Preferred scrims include those formed from polyolefins,
polyamides, polyacrylates, or polyesters, for example non-wovens,
foams or nets. Suitable non-woven scrims are available from HDK
Industries Inc. (USA). The scrim material may, for example,
comprise sodium polyacrylate fibres, such as those commercially
available under the tradename OasisTM from Acordis Technical
Absorbents Limited. The scrim is preferably provided by introducing
it into a laid down (e.g., cast) layer of a pre-gel liquid
precursor for the hydrogel material, before curing, so that the
liquid pre-gel covers and surrounds the scrim. On curing of the
liquid pre-gel, the hydrogel is thereby formed encapsulating the
scrim material. Use of a scrim material in this way is found to be
potentially helpful in enhancing the strength and ease of handling
of the hydrogel component and/or the finished dressing.
[0138] The material comprising the second layer is, but not limited
to, preferably a moisture vapour permeable non woven fibre and
includes but not limited to those formed from a material that is
natural in origin, synthetic in origin, or partly natural and
partly synthetic including but not limited to cellulose, cotton,
polyolefins, polyamides, polyacrylates, or polyesters. Suitable
non-woven materials are available from Fibreweb Tecnofibra S.p.A.
(Italy), for example Tecnojet B-650. The non-woven density has a
density greater than 50 and less than 500 g/ml.
[0139] The third layer preferably comprises a material with a
tensile strength greater than 15 N/25 mm, more preferably greater
than 25 N/25 mm and even more preferably greater than 35 N/25 mm.
It additionally comprises a percentage elongation to break greater
than 100, more preferably greater than 200 and even more preferably
greater than 400. The material also comprises a medical grade
adhesive coated on one side with a coat weight greater than 10
g/m.sup.2, more preferably greater than 20 g/m.sup.2 and even more
preferably greater than 30 g/m.sup.2 but preferably less than 100
g/m.sup.2. Preferably the material comprises a polyurethane and
more preferably comprises a polyurethane film/foam composite,
Suitable materials for the third layer are available from Exopack
(UK). A suitable example is Inspire 7235.
[0140] The fourth layer preferably comprises a flexible film which
can be formed from a material natural or synthetic in origin and
includes but not limited to polyolefins, polyurethanes, polyamides,
polyacrylates, or polyesters. The material preferably has a tensile
strength greater than 10 N/25 mm and more preferably greater than
15 N/25 mm. The elongation to break is preferably greater than 100%
more preferably greater than 250%. Suitable materials are available
from Exopack UK, for example Inspire 2301, a cast polyurethane
film.
[0141] Where an optional fifth layer is used, as described above,
this optional fifth layer preferably comprises a double sided
adhesive coated film. The adhesive is preferably a hypoallergenic
pressure sensitive adhesive with a peel strength adhesion to
stainless steel preferably greater than 3 N/25 mm, more preferably
greater than 5 N/25 mm but less than 25 N/25 mm. Suitable materials
are available from 3M (US). A suitable example is 3M Double Coated
Medical tape Product Number 1522.
[0142] The construction of the dressing of the present invention is
designed to allow excellent adherence to the body when applied in a
wide variety of environmental conditions. These include, desert,
tropical rain forest and arctic conditions. The dressing will also
remain adherent in the presence of body fluids including blood. The
flutter valve will close (i.e., form a seal) with a slight negative
pressure. Typically the pressure in the intrapleural cavity is 4 mm
Hg (or approximately 5 cm H.sub.2O) less than the pressure in the
alveoli of the lungs (which always equalizes with the atmospheric
pressure outside of the body). It is this negative relative
pressure in the intrapleural cavity that keeps the lungs from
collapsing during expiration. On inspiration the intrapleural
pressure decreases by about 3 cm H.sub.2O to 5 cm. H.sub.2O To form
a seal on a penetrating chest wound on inspiration the flutter
valve must therefore become operational with a negative pressure
not greater than 5 cm H.sub.2O, preferably less. This will also be
reflected in the rate of decrease in pressure. It has been found
that prior art dressings tested in vitro (a rectangular metal box
with an internal volume of circa 3.8 litres with a centrally placed
hole (circa 4.5 cm.sup.2) over which the dressings are mounted)
require a much higher and sustained air removal flow to achieve a 5
cm H.sub.2O pressure reduction as measured by a water manometer
connected to the 10 mm external diameter tube used to evacuate the
air in the box. The flutter valve construction also requires
minimal negative pressure to seal in the presence of fluid.
[0143] Use of Certain Hydrogels in Chest Seal Dressings
[0144] The use of certain ones of the above specifically identified
hydrogels in dressings for use in dressing penetrating chest wounds
is itself new and therefore constitutes a further aspect of the
present invention.
[0145] This further aspect is itself inventive whatever the number
and construction of the one-way valve(s), because the use of these
particular hydrogel skin adhesives had not at all been considered
for use in this area of trauma treatment, despite long existence
and recognition in the hospital and clinical environment. The
present inventors have realised for the first time that certain
highly engineered hydrogels in fact are robust enough and suitable
for field conditions such as chest trauma, and can play an
extremely valuable role in saving lives under those conditions.
[0146] Therefore, in a further aspect the present invention
provides a dressing for covering a wound of a patient suffering
from a penetrating chest wound, comprising a sheet member adapted
to be adhered to the patient's skin in use to provide an airtight
seal around a space defined by the dressing over the wound, and at
least one valve permitting one-way air, blood and/ or other fluid
flow communication from the space above the wound to the exterior
of the dressing, wherein the sheet member is adapted to be adhered
to the patient's skin in use by being provided with a skin-adhesive
coating comprising a hydrated polymer formed by polymerisation of
one or more monomer selected from olefinically unsaturated
aliphatic or aromatic vinyl sulphonic acids, vinyl sulphobetaines,
acrylic and methacrylic sulphonic acid esters, 2-hydroxy-3-acryloxy
propyl sulphonic acid, 2-hydroxy-3-methacryloxy propyl sulphonic
acid, 2-acrylamido-2-methyl-propanesulphonic acid and salts
thereof.
[0147] The dressing according to this further aspect may be used in
conjunction with any one or combination of the features, examples
and embodiments described herein in relation to other aspects of
the invention.
[0148] General Applicability of Described Features Etc.
[0149] Where, in the discussion herein, a feature or example or
preference has been described in relation to one aspect of the
invention, it will be understood that it is equally applicable to
describing the corresponding feature or example or preference in
relation to each of the other aspects of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0150] The invention will now be described further, without
limitation and purely by way of example, with reference to the
accompanying drawings, in which:
[0151] FIG. 1 shows a top view of a wound dressing;
[0152] FIG. 2 shows a schematic cross-section along the line A-A of
FIG. 1, looking in the direction of the arrows;
[0153] FIG. 3 shows a schematic view of a test chamber for testing
the performance of the wound dressing of FIGS. 1 and 2; and
[0154] FIG. 4 shows a top view of a spacer device suitable for use
with the wound dressing of FIGS. 1 and 3.
DETAILED DESCRIPTION OF THE DRAWINGS
[0155] In FIG. 1, features that are invisible from above (unless
the layers or some of them are transparent or translucent) are
depicted in dotted lines. For clarity, however, the tags 16 and 17
of the release sheet 15 are not shown in FIG. 1.
[0156] Referring to FIGS. 1 and 2, there is shown generally an
embodiment of a multilayered wound dressing structure comprising
five main layers 10, 11, 12, 13 and 14.
[0157] Layer 10 comprises a water absorbent gel, preferably a
hydrogel, that in use contacts the skin area surrounding the wound.
It optionally comprises one or more porous scrims.
[0158] Layer 11 comprises a backing material, for example a
breathable non-woven material.
[0159] Layer 12 comprises a foam/film composite material with an
acrylic adhesive coated on to the wound-facing face.
[0160] Layer 13 is a flexible film acting as an upper movable layer
serving a plurality of flutter valves, as will be described in
greater detail below.
[0161] Layer 14, which may be omitted or replaced by alternative
means of securement between layers 11 and 13, is a film coated on
both sides with an adhesive.
[0162] In this embodiment a conventional release sheet (e.g., of
siliconised paper or non-stick plastic) constitutes a bottom layer
15, not counted in the five mentioned above. This release sheet is
split into two parts in conventional manner, to provide a pair of
pull tags 16, 17 by which the release sheet can be grasped for
peeling off.
[0163] Overlain over the upper surface of the bottom layer 15, and
provided with a central aperture 1 where the wound will be in use,
is the first layer of the dressing, constituted by a skin-adhesive
layer 10.
[0164] Overlain over the total upper surface of the skin-adhesive
layer 10, and also provided with a corresponding aperture 1 where
the wound will be in use, is the second layer, constituting a
backing material layer 11 for the dressing. This layer 11 provides
mechanical support to the skin-adhesive layer and prevents the
upper surface of the skin-adhesive layer 10 from sticking to
external objects in use. The backing material is suitably chosen
for strength and lightness, as well as flexibility and
skin-conformability, and to provide a pleasant touch sensation when
touching the external surface of the dressing directed away from
the skin.
[0165] Overlain over a region (in this embodiment not the total
area 0 of the upper surface of the backing material layer 11 is a
third layer 12 which provides an anchor for sealing the fourth
layer 13 (described below) that forms the moveable parts of the
flutter valves. The third layer 12 of the dressing is provided with
an aperture generally corresponding to the aperture 1 of the first
and second layers where the wound will be in use. However, the
aperture in the third layer is smaller than the aperture 1 in the
first and second layers described previously, so that a flange 2 of
the material of the third layer extends into the aperture 1 of the
first 10 and second 11 layers around its periphery, by a distance
of about 0.2 to about 1 cm, preferably about 0.5 cm. By selecting
the material of the third layer 12 to be of suitable flexibility,
and providing a suitable skin-adhesive coating on the underside of
the flange 2, the flange can in use stick to the skin surrounding
the wound and thereby enhance the air-tight seal around the wound
as well as restricting direct contact between blood and other wound
fluids and the skin-adhesive of the first layer 10.
[0166] The skin-adhesive of the flange 2 provided by the third
layer, as described above, is protected before use by the release
layer 15 mentioned above.
[0167] The fourth layer 13 overlies the upper surface of the third
layer 12, and is formed of a thin film having sufficient
flexibility to serve as the moveable portions of the plurality of
flutter valves. This layer has no aperture corresponding to the
apertures of the first to third layers mentioned above, but instead
a plurality of holes 3 near its periphery, these holes being
dimensioned and arranged to serve in use as the mouths of the
flutter valves. The fourth layer 13 is non-adhesive on both major
faces, and is sealed to the upper surface to the third layer 13 in
a seal line 4 around its periphery, ensuring that the holes 3 are
free to open and close in use in flutter valve manner, cooperating
with the underlying portion of the upper surface of the third layer
11.
[0168] The seal line 4 in the illustrated embodiment is provided by
the fifth layer 14, which is composed of a strip of double-sided
adhesive film arranged under the border of the fourth layer 13.
[0169] The holes 3 of the fourth layer as illustrated are circular,
but may be shaped in any convenient way to have minimal sharp
corners of other points where the material of the fourth layer 13
can become stressed during working of the flutter valves.
[0170] The layers are suitably secured together by appropriate
conventional means, for example gluing, melt-welding, heat welding,
ultrasound welding, or any combination thereof. Of course, where a
layer has its own adhesiveness, it may be adhered directly to an
adjacent layer.
[0171] As illustrated in FIG. 2, a gap is shown between layers 11
and 13. However, this is simply to show more clearly the
arrangement of the fifth layer 14 which provides the seal line 4
around the periphery of the fourth layer 13. In practice, the layer
13 will be quite tight and the parts of it that lie between a hole
3 and the central region of the dressing will lie flat and in
contact with the upper surface of the third layer 12. Only when
there is an overpressure of air, or liquid, in the space 5 defined
above the wound in use will the fourth layer 13 move apart from the
upper surface of the third layer 12. However, when there is no
overpressure, or an underpressure in the space 5 defined above the
wound, the fourth layer 13 will be pressed against the upper
surface of the third layer 12 by the tautness of the fourth layer
13 and/or by external atmospheric pressure, so providing the
flutter valve action according to the present invention.
[0172] Referring now to FIG. 3, there is shown a schematic view of
a test chamber 18 used for evaluating the chest seal performance of
wound dressings, including but not limited to the dressing
illustrated in FIGS. 1 and 2.
[0173] The test chamber 18 comprises a stainless steel box 19, for
example of dimensions 270 mm.times.270 mm.times.60 mm (providing a
4.2 litre internal volume), with a rectangular opening in the top
of the box onto which is placed a stainless steel plate 20 which is
removably held in position by adjustable clamps, not shown, which
clamp the plate 20 to a rubber seal (not shown) which extends
airtightly between the plate 20 and the top portion of the box 19.
For use with the stated 4.2 litre box the plate suitably has
dimensions 260 mm.times.200 mm.times.2 mm and the rectangular
opening of the top of the box 19 is only slightly larger than 260
mm.times.200 mm. The plate 20 which has a circular orifice 21,
suitably about 28 mm in diameter, centrally located. In this way,
the size of the orifice 21 can be adjusted as desired, by using a
range of plates 20. An air inlet/outlet port 22 leading to a
suitable pump (not shown), for example a bellows pump, and a
pressure gauge port 23 leading to a conventional pressure gauge
having a typical range of -40 cm H.sub.2O to +40 cm H.sub.2O)
(pressure gauge not shown) are located on one side of the chamber
18 and air-flow communicate between the interior of the box 19 and
the respective pump or gauge.
[0174] Referring finally to FIG. 4, there is shown a top view of a
spacer device 24 suitable for use with wound dressings, including
but not limited to the dressing illustrated in FIGS. 1 and 2.
[0175] The illustrated spacer device 24 is constructed as a
complete ring of rigid internally corrugated sheet material, for
example an internally corrugated plastic sheet, having continuous
major faces spaced apart by the internal corrugations with a
face-to-face thickness about 0.25 cm. An adhesive is provided on
the lower major face (not shown) so that the spacer 24 can be stuck
to the face of the dressing that is directed away from the
patient's skin in use. The internal corrugations are shown by
dotted lines 25 in FIG. 4 (although the corrugations are shown for
only a portion of the device 24, they will correspondingly be
present over the whole device).
[0176] The spacer device 24 is illustrated at approximately full
size for use with a typical adult human chest seal dressing
according to FIGS. 1 and 2, so that the ring will encircle all the
flutter valves 3 of the dressing. The ring has a shape
corresponding generally to the shape of the dressing, but a little
smaller than the outside limits of the dressing. The internal
corrugations 25 of the spacer device 24 provide through-holes
between the radially inward and radially outward sides of the ring,
which allow air, blood and other fluid to pass from the encircled
region above the flutter valves 3 to the external atmosphere when
the spacer is in place on the dressing, when an external object
such as clothing, a blanket or a thermal insulating sheet is laid
over the dressing and spacer.
EXAMPLES
[0177] The present invention will now be further illustrated with
reference to the following non-limiting Examples.
Example 1
[0178] This Example shows particular materials and a method by
which the embodiment of the dressing illustrated in FIGS. 1 and 2
may be constructed.
[0179] First Part
[0180] First Layer 10
[0181] A 200 mm by 150 mm sample cut from an adhesive hydrogel with
an integral non-woven scrim made in accordance with the above
description, designated as FW 206, available from First Water Ltd,
UK).
[0182] Second Layer 11
[0183] A 200 m by 150 mm sample cut from a non-woven material
(Tecnojet B-650, Fibreweb Tecnofibra S.p.A. (Italy)).
[0184] Layer 11 was laminated to layer 10 and then a centrally
located 40 mm by 40 mm diamond shaped aperture 1 was cut through
both layers.
[0185] Second Part
[0186] Third Layer 12
[0187] A centrally located 35 mm by 35 mm diamond shaped aperture
was cut into a 110 mm by 100 mm polyurethane film/foam composite
(Inspire 7235, Exopack, UK).
[0188] Fourth Layer 13
[0189] Four circular 12.5 mm diameter apertures were cut into a
cast polyurethane film, Inspire 2301, Exopack UK. The apertures
were located with the centres 25 mm from the outer edge of the
layer along the line between diagonally opposed corners.
[0190] Fifth Layer 14
[0191] A centrally located 90 mm by 80 mm aperture was cut into 110
mm by 100 mm double sided adhesive polyethylene film, Double Coated
Medical tape Product Number 1522 (3M, US).
[0192] The dressing was assembled by placing layer 12 onto the
laminate formed in the First Part, such that the perimeter of the
apertured area of layer 12 overlapped into the aperture 1 through
the laminate. Then layer 14 was placed onto layer 12 such that
layer 14 surrounds the aperture in layer 12. Finally, layer 13 was
placed onto layer 14 such that the apertures in layer 13 were
within the aperture in layer 14. A small amount of pressure was
applied to assist in the lamination of the layers.
[0193] The finished assembly was mounted on a release sheet 15 and
packaged for storage and transportation.
[0194] The final assembled dressing was able to allow the flow of
air and fluid in the direction of layer 10 to layer 13 but
prevented the reverse flow.
Example 2
[0195] This Example describes the testing process and test data
relating to the dressing of the present invention.
[0196] Test Method
[0197] To test the performance of the chest seal dressing
illustrated in FIGS. 1 and 2 and constructed as described in
Example 1, and to compare it against dressings of the prior art,
the test chamber 18 as illustrated in FIG. 3 was used.
[0198] A dressing to be tested is placed on the removable plate,
held in place by the adhesive present on the dressing, with the one
way valve assembly of the dressing centrally positioned over the
orifice 21 in the removable plate 23.
[0199] A known volume of air in excess of the volume of atmospheric
air starting in the test chamber 18 (for example, selected from a
range of 50 cc to 500 cc) is then pumped in and out of the chamber
18 by means of the pump, at a known rate (for example, selected
from a range of 2 to 40 cycles (in and out is one cycle) per
minute. The pressure inside the chamber 18 is constantly monitored
by the pressure gauge, which suitably has a measurement range
encompassing -40 to +40 cm H.sub.2O. If the valve system of the
dressing closes effectively on removal of air from the chamber then
the pressure inside the chamber will decrease. Measured values of
decrease at less than about -20 cm H.sub.2O are indicative of the
formation of a good seal.
[0200] When air is pumped into the chamber the pressure will
increase until such time as the one way valve system of the
dressing opens. It is this valve opening pressure that is of
critical importance in the performance of a chest seal dressing. If
the valve opening pressure is too high, it is possible that during
the breathing cycles of a patient with a penetrating chest wound
the valve will not open and consequently this would increase the
risk of a tension pneumothorax.
[0201] In the tests below a test chamber was used in which the
dimensions of the box 19 were 270 mm.times.270 mm.times.60 mm
(providing a 4.2 litre internal volume), the dimensions of the
plate 20 were 260 mm.times.200 mm.times.2 mm, and the diameter of
the orifice 21 was 28 mm in diameter. The excess air in/out volume
was 400 cc and the pump rate for this was 30 cycles per minute.
[0202] Sample dressings (a) as described above in Example 1
according to the present invention, (b) the marketed Hyfin Vent
Chest Seal (North American Rescue LLC, Greer, S.C., USA;
http://www.narescue.com/HyFin_Vent_Chest_Seal-CNB3327DB2521D.html?BC=3C74-
57EA9AFA), (c) the marketed Bolin Chest Seal, and (d) the marketed
Asherman Chest Seal were tested using the test system described in
the preceding paragraph for a two hour period. The test results are
shown below.
[0203] Test Results
[0204] All the dressings tested produced a pressure in the chamber
on evacuation of air over the test period of on average less than
-30 cm H.sub.2O, indicative of the formation of a good seal.
However the average valve opening pressures were different as shown
in the table below.
TABLE-US-00001 Average Opening Standard Dressing Pressure (cm
H.sub.2O) deviation (a) Present Invention +0.4 0.2 (b) Hyfin Vent
Chest Seal +8.8 1.2 (c) Bolin Chest Seal +9.9 2.4 (d) Asherman
Chest Seal +2.6 0.2
[0205] The data show that the dressing of the present invention has
significantly lower opening pressure than commercially available
prior art.
[0206] The foregoing broadly describes the present invention
without limitation to particular embodiments. Variations and
modifications as will be within the abilities of those skilled in
this art are intended to be included in the scope of this invention
as defined in and by the appended claims.
* * * * *
References